The present invention relates to inkjet printing, and in particular to a specific ink set with combinations of light and dark dye load of a given color for improving inkjet image quality.
Color inkjet printers typically use three inks of differing hue: magenta, yellow, and cyan, and optionally black. The particular set of colorants, e.g., dyes, used to make the inks is called a xe2x80x9cprimary dye set.xe2x80x9d A spectrum of colors, e.g., secondary colors, can be generated using different combinations of the primary dye set.
A successful ink set for color inkjet printing must be compatible with the inkjet pen and printing system. Some of the required properties for the inkjet ink include: good crusting resistance, good stability, the proper viscosity, the proper surface tension, little color-to-color bleed, rapid dry time, no negative reaction with the vehicle, high solubility of the dyes in the vehicle, consumer safety, low strike through, high color saturation, and good dot gain.
Furthermore, the colored characteristics of the colorants play an important role in the quality of the printed inkjet image. Up to the present time, color inkjet inks have been designed and tailored for printing business graphics such as depiction of information in the form of xe2x80x9cpie-chartsxe2x80x9d and xe2x80x9cbar-chartsxe2x80x9d on plain paper. These applications require that inkjet use bright, vivid, high chroma colorants that, in general, are neither lightfast nor resistant to air fade.
One attribute that is particularly important in imaging (i.e., color rendition of pictures) is xe2x80x9cgrainxe2x80x9d. Grain describes how visible the dots are to the viewer. If large, dark drops are used, the dots become very visible and image quality is degraded.
One technique to reduce grain is to use smaller drop weight to produce nearly invisible drops. The down side to this technique is the need for more difficult and more costly manufacturing processes due to the requirement for smaller orifice holes and resistors and more difficult reliability challenges due to the smaller holes.
Another technique is to use additional xe2x80x9clightxe2x80x9d inks such as a light magenta or cyan at colorant loadings 5-25% of the normal or dark ink. This technique allows the use of larger, low colorant load drops. These xe2x80x9clightxe2x80x9d drops are less visible due to the presence of less colorant. One downside to this approach is that these xe2x80x9clightxe2x80x9d inks fade much faster on media than the dark inks. This fade often occurs in critical areas such as the skin tone in a picture of a human being. Thus, there is a need for more lightfast and air fade resistant colorants to be used in these light inks.
The present invention relates to an ink set for ink-jet printing, wherein at least one ink of the ink set comprises a light dye load and a dark dye load, both the light dye load and the dark dye load being one color, the one color being selected from the group consisting of magenta, cyan, yellow and black; and the light dye load being at least one of air fade resistant, light fade resistant and humid color migration resistant.
The present invention also relates to a method for inkjet printing, the method comprising the step of ejecting ink from an inkjet, the ink comprising a light dye load and a dark dye load, both the light dye load and the dark dye load being one color, the one color being selected from the group consisting of magenta, cyan, yellow and black; and the light dye load being at least one of air fade resistant, light fade resistant and humid color migration resistant.